Tire grooving apparatus



Nov. 21, 1944. E. 1. BlVANS 2,362,957

TIRE GROOVING APPARATUS Filed March 9, 1942 11 Sheets-Sheet 2 M r VlNvEhg'roR f/berf L 50 0/75 4 BY ATTORN EY Nov. 21, 1944.

E. L. BIVANS TIRE GROOVING APPARATUS Filed March 9; 1942 llSheet'S-Sheet 3 VI 5 on w m R N o EfiJ ffl v4 N/ A f Nov. 21, 1944. E.L. BIVANS TIRE GROOVING APPARATUS Fiied March 9, 1942 11 Sheets-Sheet 4INVENTOR f/ erfLfilra/zs BY ATTORNEY Nov. 21, 1944. E. L. BIVANS TIREGROOVING APPARATUS Filed March 9, 1942 11 Sheets-Shet 5 at kw I." .& IE:

INVENTOR f/bcrf LE 670$ BY W ATTORNEY Nov. 21, 1944. E. L. BQIVANS TIREGROOVING APPARATUS Filed March 9, 1942 11 Sheets-Sheet 6 /7/- INVENTORATTO RNEY Nov. 21, 1944. E. L.. BlVANS TIRE GROOVING APPARATUS 11-Sheefs-Sheet 9 Filed March 9, 1942 w R Y m w o m m a M V R #1 w m a mf 5l 4 V T A W 7 M m A Nov. 21, 1944. E. L. BIVANS TIRE GROOVING APPARATUSIll Sheets-Sheet 11 Filed March 9, 1942 \NVENTOR E/berf L, 5/3 0075 BY wvATTORNEY Patented Nov. 21, 1944 UNlTED STATES PATENT ornce 'rmr. caoovmoAPPARATUS Elbert Litton Bivans, Los Angele s, Calif., assignor to ArchB. Cleveland, Los Angeles, Calif.

Application March 9, 1942, Serial No. 433,954

12 Claims canizing the camelback to the tire, and to cure it. In onesuch process, the vulcanization is accomplished by the aid of livesteam, inert gas or other heat transmitting media, directly in contactwith the tire.

Before or after this vulcanization is completed, the grooves are cut toform the tread pattern.

The cutter is preferably in the form of a grooving knife, heated as byelectricity. This knife is urged in a generally radial directioninwardlyof the tread, thus determining the depth of the groove to becut; at the same time the tire is rotated, was to cause relative angularmotion between the tire and the knife. In the past, it has been commonto guide the knife mainly manually. This of necessity introducedundesirable irregularities.

It is one of the objects of this invention to provide an improved groovecutter apparatus operated substantially by machinery, and ensuring thatthe grooves will conform to the desired pattern.

It is often desired. to cut grooves to form a pattern, rather thanstraightunswerving grooves. For example, V shaped offsets may bedesired, at uniformly spaced points along the groove. The apparatus ofthis invention makes it possible not only to out such patterns withoutthe necessity of hand guiding, but also to provide a variety of patternsby appropriate adjustment of the apparatus. v

In order to accomplish these results, the apparatus incorporates acarriage or head that supports the grooving knife. This carriage ismovable in a direction parallel with the axis of the tire, uponappropriate guides. It is another object of this invention to provide amechanism that will automatically and intermittently move this carriagein that direction simultaneously with the rotation of the tire, to causethe groove to assume a transverse direction. 7

Several problems occur in connection with the automatic intermittentmovement of the groover head. The groover tool that is found to be quiteeffective is one that is heated by the aid of electric power, and isU-shaped. There is a forward or cutting edge for the tool, correspondingin configuration to the letter U, so that a cutting is secured, definedby the legs and bottom of the U. In performing its cutting operation,this edge must be presented to the work so as to lie in a planesubstantially normal to the direction of relative motion between thetool and the work. Accordingly at the beginning of the lateral movementof the carriage in one direction, the tool must be turned to agree withthe change of direction of the cut. It is accordingly another object ofthis invention to make it possible to maintain the position of thegroover tool in relation to the direction of the out, either when thegroove is undeviating, or when there are transverse portions or offsetsfrom the groove.

It is still another object of this invention to make it possible topredetermine the size, or position, or the number of such transverselycut portions of the groove.

It is usually desirable to cut a number of grooves in the tread portionof the tire. These grooves are disposed along the width of the tire in adefinite spaced relation. It is another object of this invention to makeit possible to out such multiple grooves in succession by appropriateadjustment of the mechanism.

The shape of the tread cross-section, taken along a plane passingthrough the axis of the tire, is rounded. Now if multiple grooves are tobe cut, spaced along this cross section, it is evident that the centerline of each of the groove sections should be normal to the treadsurface where the groove occurs. This requires that the groover knife beangularly adjusted iroinfone cut to the next. It'is another object ofthis invention to make it possible to effect this ad'j'u'stment in anautomatic manner, as the position of the groover is adjusted for thesucceeding grooves.

The groover knife, for this urpose is so mounted with respect to thecarriage that'the lateral position of the groover may be adjusted withrespect to the carriage. It is another object of this invention toprovide a simple mechanism that effects the angular adjustment of thegroover as this lateral adjustment is made.

It is still another object ofthis invention to provide a simple andeffective manner of heating the groover, and particularly by directlypassing a heating current through the groover.

It is sometimes desirable to provide sub-vents in the tire grooves.Thesesub -vents are formed by reducing the depth of the groove for ashort angular distance, thus stiifening the walls of the groove. It isanother object of this invention to make it possible to produce thesesub-vents by a periodic slightlift of the groover as the groovingprocess proceeds. In this connection, it is still another object of thisinvention to make it possible optionally to render the sub-ventproducing means inactive.

It is still another object of this invention to provide an adjustmentfor determining the depth of the groove made by the groover.

In a practical embodiment of the apparatus, it is desirable toincorporate the groover in a "stitcher" apparatus. Such a stitcherapparatus usually includes a supporting axle upon which a tire may bemounted for free rotation, and a power driven roller having a concaveface, adapted to engage the camel back" adhesively placed on the treadportion of the tire. As the roller is rotated, the tire is frictionallyrotated thereby, and at the same time, the camel back is firmly urgedagainst the annular periphery oi the tire carcass. Thus air bubbles aresqueezed out.

This process of "stitching is well-known, and no further explanationthereof is necessary. It is another object of this invention to providea combination stitcher and. groover, so arranged that a common source ofpower may be utilized optionally for either th stitcher or the grooveroperation.

This invention possesses many otheradvantages, and has other objectswhich may be made more easily apparent from a consideration of oneembodiment of the invention. For this purpose there is shown a form inthe drawings accompanying and forming part of the present specification.This form will now be described in detail, illustrating the generalprinciples of the invention; but it is to be understood that thisdetailed description is not to be taken in a limiting sense, since thescope of this invention is best defined by the appended claims.

Referring to th drawings:

Figure 1 is a side elevation of an apparatus embodying the invention,and shown as operating upon a tire;

Fig. 2 is a vertical sectional view of the apparatus taken substantiallythrough the axis of the tire being treated;

Fig. 3 is a fragmentary sectional view taken generally along the plane3-4 of Fig. 2;

Fig. 4 is a sectional view taken along plane- Fig. 5 is a sectional viewtaken along plane 5-5 of Fig. 3;

Figs. 6 and '7 are enlarged sectional views taken along correspondinglynumbered planes of Fig. 3;

Fig. 8 is an enlarged sectional view taken substantially along plane 8-8of Fig. 1;

Fig. 9 is a planview partly in section of a part of the apparatus takenfrom the direction of the arrow 9 of Fig. 8;

Fig. 10 is an enlarged sectional view taken along the plane IIII0 ofFig. 8;

Figs. 11 and 12 are sectional views taken along correspondingly numberedplanes of Fig. 13;

Fig. 13 is a sectional view taken along the plane I3--l3 of Fig. 9;

Figs. 14, 15, 16 and 17 are sectional views taken along correspondinglynumbered planes of Fig. 13;

Fig. 18 is a sectional view taken along plane I8-I8 of Fig. 17;

Fig. 19 is a view taken along the plane I9-I9 of F18. 18;

manner in which a heating current is transmi ted through the grooverknife;

Fig. 21 is a view of a part of the apparatus taken from the direction ofthe arrow 2i of Fig. 7;

Fig. 22 is a sectional view taken along plane 2222 of Fig. 7;

Figs. 23 and 24 are sectional views taken along the correspondinglynumbered planes of Fig. 21;

Fig. 25 is a sectional view taken along the plane 26-25 of Fig. 22;

Fig. 26 is a sectional view taken along the plane 2626 of Fig. I;

Fig. 27 is a sectional view taken along the plane 21-21 of Fig. 26;

Fig. 28 is a diagrammatic development of the carriage shifting camillustrated in Figs. 26 and 2'7; 1 v

Figs. 29, 30 and 31 are fragmentary developments of various tire treadgrooves that may be cut or formed by the aid of the apparatus;

Fig. 32 is a sectional view of a tire taken in a plane passing through agroove and illustrating a sub-vent;

Fig. 33 is a side elevation of a cam of different form from thatillustrated in Figs. 26 and 2'7;

Fig. 34 is a fragmentary development of a portion of a tire grooved bythe aid of the cam shown in Figs. 33 and 35;

Fig. 35 is a diagrammatic development of the cam illustrated in Fig. 33;

Fig. 36 shows the lines of a chart that may be utilized for facilitatingthe adjustment of the apparatus; and

Figs. 3'7 and 38 are detail sections as seen on correspondingly numberedplanes of Fig. 2.

A tire I (Figs. 1, 2, 8, 13 and 16) is illustrated as the tire uponwhich the grooves are being cut by the aid of the apparatus. For thispurpose the tire is mounted so as to be driven about an axis 2 (Figs. 1and 2) shown in this instance as horizontal. As shown most clearly inFigs. 1 and 2, the road engaging surface 3 is shown as prepared for thegrooving operation. This road engaging or tread surface 3 may have beenformed on the tire as heretofore explained as by vulcanizing a strip ofcamel back on the outer periphery of the tire that had been machineddown on its periphery to accommodate the "camel back; or the tire maybeen entirely new carcass, formed with a smooth outer periphery.

As the tire I is rotated at a relatively low v speed about the axis 2, agroover knife 4 (Figs.

8, 1.3 and 16) is caused to form the groove 5 by cutting out the strip Iof the rubber. This strip I is shown most clearly in Figs. 8, 13 and 16.

In order to effect this result, the groover knife 4 is shown as ofgenerally U-shape made from metal capable of maintaining a sharp edge.Legs 8 and 9 of the knife extend substantially parallel to each other,and in a direction parallel to the sides of the groove being formed.That edge I0 (Fig. 13) which is presented to the rubber of the tire Imay be quite sharp. The entire groover knife 4 is arranged to be heated.so as to facilitate the cutting of the rubber to form the strip I. Asshown most clearly in Fig. 8, the groover knife 4 is arranged so thatits cutting edge lies in a plane substantially normal to the directionof movement of the tire I with respect to the groover knife 4. Thismovement is in a clockwise direction as viewed in Fig. 8

' and as indicated by the arrow I I thereon.

Fig. 20 is a wiring diagram illustrating the The cutting of the groove 5may occur in such a way as to provide a straight groove extendingcircumferentially in the tread portion of the tire; or as will behereinafter described, the groover knife 4 may be so controlled as toprovide changes in the direction of the knife to form oblique portionsor notches in the groove, in accordance with a pre-con'ceived pattern.

In order to ensure sufficient resistance of the rubber of the tireagainst deformation while the groover knife 4 is in operation, it isdesirable to provide the usual inner tube I2 (Fig. 2) within the tirecasing I, and to inflate it to a sufficient degree to attain this end.Furthermore, as illustrated in Fig. 2, the tire I is mounted by the aidof a stationary standard I3 forming the main support for the entireapparatus.

This entire apparatus includes a stitcher mechanism. The stitcher or thegroover may optionally be caused to operate upon the work. The stitchermechanism includes the concave faced stitcher roller I4. This roller hasan axis 59 parallel to the tire axis 2. It contacts the peripheral treadportion of the tire; but optionally it may be driven by the aid of asource of motion to effect the stitching operation. During the groovingoperation, this roller serves as a rolling abutment with which theperiphery of the tire is in frictional engagement. The roller I4 is freeto turn by the friction imposed upon it by rotation of the tire I aboutits axis 2. Furthermore, as will be hereinafter explained, the axis 2 ofthe tire I may be adjusted with relation to the machine so as to bringthe tire I into proper cooperative position with the groover ,knife 4.This position is determined by movement of the axis 2 verticallydownwardly or upwardly until the stitcher roller 14 comes into contactwith the outer periphery 3 of the tire I. In this way, a wide range oftire sizes may be accommodated by the apparatus.

The standard I3, as shown most clearly in Figs. 1, 2, 3, 4 and 5, isshown as a casting extending generally vertically upwardly. The lowerportion of the casting is of ribbed construction and may be formed witha foot or base 4I4 adapted to rest upon the floor 5. In order to providethe means for adjustment of the position of the tire axis 2, the lefthand portion of the standard I3 is formed with the vertical guides I5(Figs. 2, 3 and 5). These vertical guides are shown as cooperating withthe guide bars I6 to form vertical grooves within which the edges of a.vertically movable slide Il may be accommodated.

Slide II carries an integral hub I6. .Within this hub is fixed astationary shaft I9 (Figs. 2.

3 and 3'7). This shaft I9 serves as a journal bearing for a sleeve 20,extending toward the left as viewed in Fig. 2. The shaft I9 extendscompletely through and beyond the tire I. This tire I is removablycarried by the rotary sleeve 26, in order to impart rotation to thetire. For this purpose left hand portion of sleeve 20 is provided withaflange 2I, which abuts a shoulder 420 formed on sleeve 20 and isprevented from rotating on the sleeve by means of a key 42I. Abuttingagainst the left hand surface of this flange 2| is the tire carryingdisk 22 having a rim 23 in which the tire is accommodated. This disk 22is appropriately apertured so as to be accommodated upon the shoulder 24extending beyond the shoulder 420.

The tire disk 22 is held flrmly in place by the aid of the nut 25threaded on a threaded extension 26 of the sleeve 20. It may bemanipuiated for example as by the aid of the handle 21. This handle isalso shown in Fig. 8. The nut 26 serves to urge a collar or washer 26against the left hand surface of the disk 22. In order further to ensureagainst relative angular motion of the sleeve 20 and the disk 22, one ormore dowel pins 29 may be attached to the flange 2i and are adapted toengage in corresponding apertures in the disk 22. A collar 423 securedto shaft I9 as by one or more set screws 424 serves to prevent axialmovement of sleeve 20 toward the free end of shaft I 9.

Rotation of the sleeve 20 and corresponding rotation of tire I is'accomplished by the aid of a worm wheel 30 which is arranged optionallyto drive the sleeve 20 by means of a pin 426 as shown most clearly inFig. 37. This wheel is engaged by a worm 3| splined on a vertical shaft32. In this way as the slide I1 is moved vertically, the worm wheel 30is correspondingly moved and the worm 3| is carried along with the wheel39. Rotation is imparted to the shaft 32 in a manner to be hereinafterdescribed.

The worm 3| and the wheel 30 are shown as enclosed in a split casinghaving the halves 33 and 34. This casing 33-34 is supported on hub I6 bymeans of a plurality of screws 428 passing through a hub 429, formed onthe half casing 34, and engaging hub I3. The other half 33 has a largeopening 436 which closely encircles a flange 43I formed on the end ofsleeve 26. These halves may be appropriately fastened together as by thebolts 35 shown in Fig. 3. Furthermore, the casing 33-34 is provided witha recess 36 for the accommodation of the worm 3|. The casing at thisplace is apertured for, the passage of the shaft 32. The lower end ofthe shaft 32 is shown as protected by a. tube 39 (Figs. land 3) threadedinto the casing 33-35. The end of tube 39 is closed by a cap 40.

The casing 33-34 may also carry the antif riction bearing structures 31and 31' disposed on appropriate shoulders formed at the top and bottomof the recess 38. A cover 33 is provided over the top end of theaperture through which the shaft 32 extends.

Gear 36 as clearly shown in Fig. 37 is rotatably supported on shaft I9and is axially confined between the face of hub 429 and flange 43I. Gear30 is provided with a bushed aperture 433 for accommodating pin 426. Pin426 is axial 1y slidable in a suitable bore 434 formed in flange 43I,the arrangement being such that by appropriate axial positioning of pin426 it may be caused to engage aperture 433 of gear 36 or to be freethereof, whereby sleeve 20 is lockedto gear 30 so as to rotatetherewith, or sleeve 20 is free to rotate while gear 30 remainsstationary. To maintain pin 426 in chosen position, it is provided witha cam head 436 adapted to engage either of the axially spaced transverseslots 431, 436,formed on sleeve 20. By rotating pin 426 by handle 439,head 436 is freed from slot 431 or 433 and pin 426 may be adjustedaxially to engage or disengage opening 433.

When it is desired to drive tire I by means of stitcher roller I4incident tosecuring the camelback on the tire carcass, it is essentialthat sleeve 20 be disconnected from gear 30, since if worm 3I is notpositively driven by the mechanism to be presently described, gear 30will be locked, as it is not able to drive the worm 3|. To rotate thetire in the proper direction when so driven, an appropriate reversingswitch may be provided for the motor 56.

The mechanism for moving the slide II vertically may now be described.This is accomplished by a rack and pinion mechanism. The rack 4| (Figs.2. 4 and 5) is shown as supported upon a rib 42 formed integrally withthe slide 11. Engaging this rack is a pinion 43 that .is mounted upon arotatable shaft 44. This shaft 44 as shown most clearly in Fig. 2 isappropriately Journaled by the aid of the boss 45 extending toward theright of the vertical web 46 of standard l3. Its right hand end is shownas being journaled in the journal bearing 41 formed integrally with theweb 48. This web is integrally joined to the vertical rib 46. Betweenthe two journal bearings is located the worm wheel 49 attached as by aset screw to the shaft-44. Appropriate collars are provided forrestraining shaft 44 against axial movement.

Worm wheel 49 may be manually rotated for adjusting the axis 2, as bythe aid of a hand wheel 56 provided with the radial handles 5|. The wormwheel as shown most clearly in Fig. 4 is attached to a shaft 52 mountedfor rotation in the hubs 53 and 54 projecting inwardl from the side ribsof standard l3. This shaft 62 carries the worm 55 that engages the wormwheel 49 for driving it. Appropriate collars on shaft 52 limit axialmovement thereof.

Rotation of hand wheel 50 in one or the other direction will cause theworm wheel 49 to move in one or the other direction, thereby alsorotating the pinion 43. This pinion 43 in turn engages the rack 41 andthe slide 11 is accordingly moved in a vertical direction.

Power for the rotation of the shaft 32 is derived from an electric motor56 (Figs. 1 and 2).

' This electric motor is shown in this instance as vertical and assupported adjacent the top of the standard I3. As shown most clearly inFigs. 2 and 6, the motor 56 is provided with an end bell 56' withinwhich is located appropriate gearing so that the motor serves to drive ahorizontal shaft 51. The end bell 56 is provided with a flange 58 by theaid of which the motormay be bolted to the web 46 of the standard 13.The axis 59 of shaft 51 coincides with the axis of the stitcher roller14. Web 46 may be appropriately apertured for the passage of shaft 51therethrough. Furthermore, a bearing sleeve 335 (Fig. 6) may be providedfor the left hand end of shaft 51. Stitcher roller 14 has a shaft 66adapted to be optionally coupled to the motor.

shaft 51. The shaft 60 as shown most clearly in Fig. 2 is journaled ateach end in the standards 6| and 62. These standards may beappropriately lined with a bearing metal as indicated by the sleeve 63(Fig.6).

Both of these standards are fastened to a supplemental frame 64 (Figs.1, 2, '1 and 8). This supplemental frame has appropriate downwardlydirected ribs 65 and 66 providing supporting surfaces for the standards6| and 62. This supplemental frame 64 (Figs, 1 and 8) has a U- shapedsection, the opening being directed downwardly and disposed immediatelyabove the axis 59 of the roller l4. Furthermore, the frame 64 may beprovided at its right hand edge with a flange 65' (Fig. 1) by the aid ofwhich this frame 64 may be attached to the upper extremity of thestandard 13.

The clutching means between the motor driven shaft 51 and the rollershaft 60 comprises a pair of clutch halves 66 and 61 (Fig. 6). Theclutch half 66' is shown as attached to the right hand extremity of theshaft 66. It comprises a collar having recesses and projections on itsright hand face. The clutch half 61 is splined for axial movement uponthe left hand extremity of the motor driven shaft 51. This half 61 isprovided with recesses and projections adapted to interengage with thecorresponding recesses and projections carried by the half as' when thehalf 61 is moved to the left. A shift fork 68 is utilized for axiallymoving the clutch half 61 into and out of engagement with the clutchhalf 66'. For this purpose this shift fork is pivoted between the ears69 formed integrally with the left hand wall of the frame 13 as viewedin Fig. 3. The handle portion of this shift fork extends horizontallyfrom the standard 13, for convenient manual manipulation. The fork endthereof extends through an appropriate aperture in the standard l3 andis provided with appropriate pins engaging in the groove 16 (Fig. 6)provided in the periphery of the splined clutch half 61.

In the position shown in Figs. 2 and 6, the clutch is disengaged and theroller 14 is not driven. In this position however, a sprocket wheel 11(Figs. 2, 3 and 6) is coupled to the shaft 51 by interengagement of theclutch 61 with the clutching hub 12 of the wheel 1|. This engagement isillustrated most clearly in Fig. 2. Thus by appropriate manipulation ofthe shift fork 68 either the roller 14 is driven or else the sprocket 1|is driven by shaft 51.

By the aid of sprocket wheel 1l'power is transmitted to the verticalshaft 32 that imparts rotation to the tire I. The manner in which thisis accomplished is best illustrated in connection with Figs. 3, 6 and'1.

Sprocket wheel 1| is coupled as by the chain 13 to a driven sprocketwheel 14. This sprocket wheel 14 is mounted upon the right hand end of ahorizontal shaft 15. This shaft 15 is shown as journaled by the aid ofthe bearing structures 16 and 11 disposed on opposite walls of a housing18. This housing 18 as shown most clearly in Figs. 1 and 3, has flanges19 overlying an aperture 60 in the right hand wall of the standard I3.These flanges serve as appropriate means for attaching this housing 18to the standard. The bearings 16 and 11 illustrated in Fig. '1 arelocated in an extension of the housing, placed to the left of the mainportion thereof as seen in Fig. l. The aperture 8!! permits the passageof the sprocket chain 13 into the housing 18.

Upon the shaft 15 and within the housing 16 there is rigidly attached abevel pinion 8 I. This bevel pinion 81 is shown as driving a similarbevel pinion 82 attached to the upper end of the shaft 32. A bearingstructur 83 is provided within the housing 18 for the upper end of theshaft 32.

As the tire I rotates in clockwise direction as indicated in Fig. 8, thegroover knife 4 as heretofore stated serves to cut out the strip ofrubber 1. For this purpose the groover knife 4 is supported as a part ofa groover knife structure, capable of being controlled in position so asto effect the cutting of the groove in the desired directions.

The groover knife structure is shown to best advantage in Figs. 9, 13,14, 16, 17, 18 and 19. Referring first to Figs. 16, 1'1, 18 and 19, theright hand edges of the legs of the groover knife are engaged in slots84 formed vertically in the metallic blocks 85 and 66 respectively.These blocks are shown (Fig. 1'1) as of substantially rectangular crosssection. They may be provided with additional grooves 81 to accommodatea wider groover knife if it is desired to cut a wider groove.Furthermore, these blocks project downwardly and are formed integrallywith the half round metallic bars 88 and 89. These half round bars aresupported within a sleeve 98 and are carefullyinsulated from each other.This may be accomplished for example by the layer of insulation 9|between the blocks 85 and 88 (Fig. 17) as well as by the insulationsleeve 92 located'between the bars 88 and 89 and the sleeve 88. Atransverse strip of insulation 93 (Fig. 14) is interposed between theflat faces of these bars. The bars may be held together by the aid of atransverse screw 94 (Figs. 13 and 16) which is appropriately insulatedfrom both of the bars as well as from the rectangular blocks 85 and 88thereof. No further fastening means is required for the entire barassembly is tightly encompassed by the supporting sleeve 98.

Furthermore, the bars 88 and 89 form electrical connections to theopposite legs of the groover knife 4 whereby an electric heating currentmay be passed directly through this groover knife for heating it. Thegroover knife'4 is especially designed to have the requisite resistanceto effect proper heating thereof. Electrical connections to these barsare indicated in general in Fig. 16 by the conductors 95 and 98. Theseconductors are provided with threaded ends passillustrated in Fig. 20.The heating current is provided by the aid of the step-down transfozgnerI89. The primary of this transformermay be controlled by the aid of aswitch II8 located on an accessible portion of the mechanism ashereinafter described. When the switch III! .is closed, the transformeris energized from the main III of a .commercialsource of electricalenergy. v

The groover knife structure is arranged to be axially and angularlymovable about the axis of sleeve 98. In this way the direction of thecutting edge of the knife may be altered to agree with the direction ofthe desired diagonal cut in ,the groove. For this purpose the sleeve 88within which the, bars 88 and 89 are fastened is arranged to besupported by frame structure II2 (Figs. 8, 9, 13 and 14) This frame hasan upper armI I8 extending generally horizontally through which thesleeve 98 extends. In this arm is located an appropriate roller bearingstructure II4 (Fig. 13) for rotatably supporting the sleeve- 98 and forguiding itaxially. Spaced below this ing through appropriate transverseapertures in the sleeve 98 and threaded into apertures in the bars 88and 89. The control of the current through these. conductors 95 and 96is effected manually in a manner to be hereinafter described. Theseconductors are also indicated in Fig. 1.

In order to clamp. the legs of the U-shaped knife 4 tightly into thebottom of the grooves 84, use is made of a clamping device illustratedmost clearly in Figs. 17, 18 and 19. A frame 91 is provided embracingthe lower portions of the blocks 85 and 88. The left hand 'wall of thisframe carries the metal blocks 98 and 99. These blocks may be formedintegrally with the. shanks I88 and IM of rivets passing through theleft hand wall of the frame. Appropriate insulation material representedby'the insulation members I82 and I83, is provided to insulatecompletely each of these rivets and blocks 98 so that there be no shortcircuiting of the current flowing through the knife 4.

The blocks 98 and 99 are. adapted to engage the left hand edge of theknife 4 as viewed in Fig. 17 and to urge the knife toward the right tothe bottom of the groove 94. In order to effect this clampingarrangement a clamp screw I84 (Figs. 13, 17 and 18) is provided. Thisscrew is threaded into the right hand wall of the frame 91. Its innerend is seated for free rotation in a socket I85. This socket I85 isformed in the right hand side of an extension .I86 shown as integralwith the supporting sleeve 98. This extension I88 furthermore carriesthe oppositely directed guide pins I81 adapted toengage the slots I88 onopposite sides of the frame 91. Now as the clamping screw I84 isturned-in the ap-' propriate direction, the frame 91 is urged toward theright and the clamping'blocks 98 and 98 engage the forward edge of theknife 4 and hold this knife firmly in place. a

By the aid of this mechanism theoperation of removing and replacing agroover knife is simple. It involves merely a loosening operation of theclamping screw I84 and appropriate removal and replacement of thegroover knife 4. This groover knife may of course take any desired formfor the purpose desired.

arm H3 is another arm II5 similarly provided with the roller bearingstructure I I8.

The manner in which the position of this frame structure may be adjustedin order to adjust the position of the groover knife 4 will be detailedhereinafter. For the present it is sufficient to note that this framestructure is provided with means for-limiting its movement under theforce of gravity toward the tire I.

This stopping structure is shown most clearly in Figs. 8, 12, 13 and 15.It comprises a roller II1 of slightly conical form adapted to engage atits forward edge with the periphery of the tire I in advance of thegroover knife 4. The roller H1 is mounted for free rotation about a .pinI I8 formed integrally with an arm I I9. This arm is pivoted about atransverse shaft I28 (Figs. 12 and 13) which extends through the bottomof the frame structure H2 and across a slot I2I disposed therein. Anadjusting screw I22 (Figs. 8, 13 and 14) is engaged in a threadedaperture in the lower portion of the frame I I2 and immediately abovethe arm II9. This screw may be provided with a thumb wing I23 forfacilitating manual adjustment of the screw I22. The lower end of thescrew provides a stop for the upper side of the lever II9. Gravity actsupon the frame structure I I2 to bring the contacting edge .of theroller II1 into position on tire I. As the screw I22 is turned, theframe structure H2 is correspondingly raised or lowered with respect tothe tire I. Accordingly the depth of the cut .produced .by the grooverknife 4 is determined.

The axis of rotation of groove limiting roller H1 is made transverse tothe axis of rotation of the tire I. In this way lateral movement of theframe structure II2 during the process of adjustment of this framestructure II2 along the tread portion of the tire is not hindered, theroller II1 rolling over the contiguous surface of the tire I. v 7

A movable support is provided for the frame structure .2. This movablesupport is made in such a manner that the frame I I2 can be given amotion transverse of the tire face for adjusting the transverse positionof the groover knife 4. As shown most clearly in Figs. 8, 9, 12, 13, 14,15 and 16, this frame structure includes a lower half I24 and an upperhalf I25. These halves are clamped together by appropriate bolts I26(Figs. 13 and 14) passing through the left hand The wiring diagram forthis groover knife is 7 portions of these frame members. At this leftframe II2 there is provided a similar coaxial stub shaft I23 integrallyformed with the arm 5. The bearing aperture I32 for this stub shaft I28is formed partly in the forwardly extending portion I30 of the lowerhalf I24. The upper portion of the bearing aperture I32 is formed by anextension I3I formed on the upper half I25. Extensions I30 and I3I areattached together as by the aid of the bolts I33 (Figs. 13 and 14) Theseportions I30 "and I3I embrace a guide rod I34 supported in a carriage,the structure of which will be hereinafter described. The parts I30 andI3I are so arranged that these parts are free to slide upon thetransverse guide rod I34. The rear surface of support H2 is placed closeto the contiguous surface of the frame I24-I25.

The carriage which supports the guide rod I34 and which thereby supportsthe groover knife structure for transverse motion, is illustrated tobest advantage in Figs. 9 and 11. It includes a frame having the sidearms I35 and I36 together with a transverse integral wall I31. It isbetween the forward ends of these arms I35 and I36 that the guide rodI34 is located. The arm I33 may be provided with an extension I38serving as a handle for the carriage. The switch IIO for controlling theenergization of the transformer I03 (Fig. may be conveniently located sothat its controlling button extends outwardly of this handle.

The entire carriage is arranged to be pivoted upon an axis I33transverse to the tread of the tire I and parallel to the axis of thetire. This pivot support is provided by the aid of the integrally formedbosses I40 and HI respectively on the inner sides of the arms I 35 andI36. These bosses coact with the shaft sections I42 and I43 which serveother purposes to be hereinafter described. It is suflicient for thepresent to note that the carriage structure I35i36 is permitted pivotalmovement about the axis I33. The force of gravity tends to rotate thecarriage I35-I36 in a clockwise direction so as to bring the limitingroller II1 into contact with the tire I.

When the support I24I25 is substantially central of the carriage asviewed in Fig. 9, the groover knife 4 is arranged to out a groove at thevery crown of the tread of the tire I. In order to cut additionalgrooves to the right or left of the crown, the groover knife structureis arranged to be moved laterally of the carriage I35-I36. This lateralmovement, however, must be accompanied by movement such that the axis ofthe sleeve 30, and therefore the cutting edge of the knife 4, stayssubstantially normal to the curvature of the tread portion. This isexemplifled for example in Fig. 16 where the central groove is shown asbeing cut. On each side thereof are illustrated the grooves I43 and I44.The center lines I45 and I46 of these grooves converge to a common pointalong the main center line I41 of the tire I. Accordingly lateralmovement to the right or left as viewed in Fig. 16 of the sleeve 30 withits groover knife structure is accompanied by a tilting movement of thesleeve 90 about the axis of the stub shafts I28 and I23. The manner inwhich this compound movement is efiected will now be described. For thispurpose reference may be had more particularly to Figs. 9, 12, 13 and14.

A lead screw I48 having an axis parallel to the axis of the guide rodI34 but spaced therefrom is threaded into the two halves I25 and I24. Asshown most clearly in Fig. 13, the axis of this lead screw intersectsthe axis of stub shafts I28, I23 affixed to frame II2. Rotation of thislead screw causes lateral movement of the supporting frame I24-I 25. Thelead screw is provided with a bearing in each arm I35 and I33. It isalso provided with a collar I43 attached to a hand wheel I50 (Figs. 9and 12). This collar, together with appropriate nuts engaging the lefthand end of screw I48, restrain axial movement thereof.

The hand wheel I50 is arranged to operate another lead screw I5 I spacedimmediately above the lead screw I48. This is accomplished by the aid ofthe gears I52 and I53 (Fig. 12). Gear I52 is shown as supported on. thecollar I43; gear I53 meshing therewith is shown as supported on a collarI53 joined to the right hand extremity of the lead screw l5l. This leadscrew I5I is engaged in a traveling nut I54, immediately back of frameII2. Lead screw I5I is restrained against axial movement in a mannersimilar to the restraint of lead screw I #8.

Nut I54 is provided with a transverse groove I55 serving as a guide fora pin I56. This pin I56 is attached to the upper portion of the grooverknife supporting frame II2 as by the aid of the set screw I51. If the,nut I54 were to travel in step with thesupport I24-I25, there would beno tilting motion of the support II2 about the axis of stub shafts I28and I20. Now considering Fig. 12, and assuming that the frame H2 is inthe central position of Figs. 9 and 16, then if the support I24-I 25 bemoved toward the right from the central position, the nut I54 must bemoved still further to the right in order to cause proper tiltingdirection of the frame H2 about the stub shafts I28, I23. Similarly, iffrom the central position 'of Fig. 12 the support I24-I25 be movedtoward the left, then the nut I54 must be moved at a faster rate towardthe left so as to provide the opposite inclination to the axis.

This result is accomplished by appropriate choice of gears I 52 and I53and appropriate choice of the thread pitch on the lead screws I48 andI5I. Furthermore, if lead screw I48 carries a right hand thread,obviously the lead screw I5I should be left handed because of thereversal of the direction of rotation through the gears I52 and I53.Gear I53 should have fewer teeth than gear I52 so that the lead screwI5I is rotated at a slightly faster rate than screw I 48. Since gearsI52 and I53 have small diameters, their teeth are necessarily relativelyfew, therefore for obtaining a finer differential movement, the pitchesof the threads of the two lead screws I48 and I5I differ slightly.

For example, in one embodiment, the gear I52 has thirty-six teeth andthe gear I53 has thirty teeth. Similarly, the lead screw I48 is ofthirteen pitch and lead screw I5I has fourteen pitch. For the valuesgiven, one revolution of screw I48 causes the advance of the stub shaftsI28, I23, of one-thirteenth of an inch, or .0169 inch. The correspondingadvance of pin I56 is X or .0857 inch, a differential of .0088 inch foreach revolution of the lead screw I48. The angular displacement of theframe H2 is determined by the differential as well as by the distancebetween the axis of shafts I28, I23 and the axis of pin I56.

' This pointer is arranged to cooperate with a ments of different widthsof treads and the particular number of grooves to be cut. For thispurpose an indicator point I59 (Figs. 8, 9 and 13) is fastened into thetop member I3I so as to be carried along with the supporting frame II2.

I60 mounted upon a rotatable drum I6I. The axis of this drum is parallelwith the axis I39 of the carriage I35I36. This drum as shown mostclearly-in Figs. 9 and 13 is provided with the end caps I62 and I63.Each of these caps I62 and I63 are telescoped over the chart I66 and areeach provided with tapered recesses for the accommodation of tapertrunnions. The left hand trunnion I64 is slidably mounted in the arm I35and is held resiliently against the head I62 by the aid of the leafspring I65. The right hand trunnion I66 is in the form of a screwthreaded through the arm I36, and having a knurled head I61. A knurledcheck nut I68 may be provided to maintain this trunnion screw I66 in anydesired adjustment.

The markings upon the chart I60 is illustrated in Fig. 36, which showsthe lines upon the circular chart, in developed position. This chart hasa CL nter line I69 corresponding to the central position of the grooverknife structure as illustrated in Figs. 12 and 16. The drum structureI6I-I62-I63 is made axially adjustable by aid of screw I61 in order tomake it possible for this chart center line I69 to correspond accuratelywith the crown or crest of the tire I.

The drum I6I that carries chart I69 may be manually rotated by the aidof the knurled head or cap I63. By the aid of this rotation it ispossible to choose any geometric element of the cylinder into which thechart I66 is formed, for cooperation with index I59. Specificcylindrical elements are marked by the horizontal lines I10 in Fig. 36.Each of the horizontal lines corresponds respectively to a width of thetreadover which the grooving is to extend. The uppermost line I10 forexample corresponds to a tread width of nine inches. The lowermost onecorresponds to a tread width of threeand one-half inches. Furthermore,these horizontal lines are intersected by several series of slopinglines. One such series is represented by the 'full lines I1I. This maybe of a specific color, for example red, and correspond to therequirement to cut six grooves in the tire face. This requirement issatisfied by the fact that there are six such sloping lines in theseries I19. Other sloping lines illustrated by the dash lines I69 andI12 may correspond to the cutting of five grooves in the tire face.These lines may also have a distinctive color, such as black. The dottedlines I13 correspond to four grooves, and may be of a distinctive colorsuch as green. 7

Assuming for example that the tire width is six inches and it isrequired to cut five grooves therein, the drum I6I is rotated until thatelement I14 corresponding to six inch width is immediately adjacent thepointer or index I59. The requirement that there be five grooves cutnecessitates a central groove, the pointer I59 starting upon the centerline I69 for the first groove. After this groove is cut the carriagestructure I36-I39 can be rotated out of contact with the tire I, and thehand wheel I56 may be rotated in either one or the other direction tobring the pointer at those places on element I14 where one of the dashlines I12 intersects the horizontal line I14. The groove can then be outafter this adjustment by permitting the carriage I35I36 to move downtothe active position illustrated. Succeeding grooves are cut in asimilar manner, the hand wheel I56 being rotated to bring the index I59to the point where the chosen element line I14 intersects the chosensloping line I12. Thus by proper inclinations of all of the lines I1I,I12, I13, the required spacing of the grooves for various tread widthscan be accurately represented by the corresponding points ofintersection of the lines with the cylinder elements I10.

In the operation of the apparatus, the handle I38 (Fig. 8) is broughtdownwardly to cause contact between the guide roller I I1 and therotating tire I. The switch I I9 is operated to closed position. As thetire I rotates in a clockwise direction, the groove is cut in the mannerhereinbefore described. The force of cutting operating as a reactionupon knife 4 causes the sleeve (Fig. 13) to be urged downwardly untilthe stop collar I15 contacts with the upper surfaceof the arm II5. Thisstop collar I15 as shown most clearly in Figs. 13 and 14 is held inappropriate position upon the sleeve 90 by aid of the set screw I16. Ithas another function which will be describedhereinafter.

It has been assumed that the carriage I35I36 is manually held againstaxial movement on its guide shafts I42 and I43. This is the conditionrequired when simply straight grooves are being cut. However, if thereare to be transverse po-rtions in the groove cut this is performed bymechanical oscillation of the entire carriage I35- I36 axiallywithrespect to the axis I29. This shifting occurs an integral number oftimes during one complete revolution of the tire I. These transversecuts may be in the form of diagonal lines which provide notches or otherpatterns in the grooves cut.

A typical tire tread pattern cut by this means portion I86 of the tireis shown as grooved with five grooves I8I, I82, I83, I84 and I85. Thecentral groove I83 is straight. The two side grooves I8I and I82 havetransverse portions I86 forming notches. In the other two side groovesI84 and I85, notches I81 are formed pointed in the opposite directionfrom the notches I85.

All of these notches are formed by appropriate timed or cyclicreciprocation or oscillation of the carriage I35I36.

For this purpose the carriage I35I36 is moved in this axial manner bythe aid of a cam I88- (Figs. '1, 9, 26 and 2'1) formed of thin metal,and supported by the shaft sections I42, I43. Thus, the cam isrotated onthe axis I39, by rotation of these shaft sections. Furthermore, thearrangement is such that the cam may be removed and new cams substitutedto form either a different pattern for the groove, or a pattern of theopposite hand. v

Shaft sections I42, I43 are driven in synchronism with the tiresupporting sleeve 20 (Fig. 2). The ratio of the rotation of shafts I 42,I43 and of the rotation of tire I is made an even integer by appropriatechoice of the gearing. Furthermore, this integral ratio may be varied bychanging the gear ratios. Under any circumstances the angular spacingbetween the notches in the grooves is independent of the tire diameter,for this spacing is dependent solely upon this integral ratio. Thisratio in most instances may be from fifteen to twenty-four,corresponding to the num-v ber of equidistant notches formed in eachgroove.

The manner in which this integral ratio drive is accomplished will bedescribed hereinafter. At this time the manner in which the cam I88 issupported upon the shaft sections I42 and I43 for ready detachabilitywill be described.

The left hand end of shaft I43 has a threaded extremity I89 (Fig. '7).It also carries a socket member I98 firmly attached to the shaft. Intothis socket member is adapted to telescope the hollow sleeve I III thatis internally threaded to engage the threaded portion I89. This sleeveI9I is formed integral with a hub I92 attached as by the aid of thetaper pin I93 to the shaft section I42. The cam I88 is provided with acentral aperture I94 through which the sleeve I9I extends. Thus the camis held between the contiguous faces of the members I89 and I92.Furthermore, in order to prevent any angular rotation between the shaftI43 and the cam I89, the socket member I98 may be provided with a pinI95 adapted to engage in the slot I98 opening into the aperture I94.

In order to remove or replace the cam I88 therefore, the hand knob I91(Figs. 1 and 7) attached to shaft section I 42 may be rotated todisengagev the threaded parts I 9I and I89. The shaft section I42 maythen be moved axially to release the cam I88. A reverse operation may beprovided for replacement of the cam I88 in an obvious manner. I

The shaft section I42 is shown as journaled in a standard I98 (Figs. 1and '1). This standard may be attached in an appropriate manner to onewall of the supplemental frame 84.

The shaft section I43 may be rotatably supported by the roller thrustbearing structures I99 and 288 (Fig. '1). These thrust bearingstructures have outer races supported in the bearing hub 28I projectingfrom the left of the housing 18 and formed integrally therewith. Acollar 282 may be attached to the left hand end of the hub 28I tomaintain the bearing structure I99 and 288 in proper axial positionwithin the hub.

Shaft section I43 has an extension 283 passing through the casing member18, and is adapted to be driven by transmission mechanism to behereinafter described. In the present instance, the cam I88 is shown asprovided with a raised crown portion 284 (Figs. 9, 26 and 27). Thecarriage I35--I38 is provided with cam follower members 285 and 288contacting opposite sides of the cam, as shown most clearly in Figs. 9and 10. Accordingly as the raised crown portion 284 passes between thecam followers 285 and 288 the entire carriage I35-I38 moves toward theleft, and then moves to the right, back to the central position.

For the accommodation of the cam followers 285 and 288, the carriageI35I36 carries a U-shaped-support 281 (Figs. 8, 9 and The cam followers285 and 288 are shown as being the rounded ends of the screws 288 and289 engaging the threads within the bosses 2I8 and 2| I. These bossesproject inwardly from the sides of the frame 281. These cam followersare mounted on a common axis 2I2 parallel with, but spaced from the axisI39 of the cam I88. Furthermore, as is apparent from Fig. 2'1, the crownportion 284 is so formed as to be in accurate contact with both of thefollowers when this crown portion moves angularly between them; that is,the thickness of the cam measured in the direction of the follower axisM2 is just sufficient to be in engagement with the cam follower points285, 288. The screws 288 and 289 are axially adjustable within thebosses 2I8 and 2| I so thatthey may be set accurately with relation tothe cam. Furthermore, they may be held gnaadjusted position as by aid ofthe check nuts The crown portion 284 of the cam thus urges theU-shapedirame 281 toward the left and toward the right in accordancewith the configuration of this crown portion. As shown most clearly inFig. 27, this crown portion 288 is so arranged that the amount oflateral movement of the carriage I35-I38 is dependent upon the distanceof the axis 2I2 of the followers from the axis I39 of the cam.Accordingly this crown portion converges toward the cam axis, as shownin Fig. 27. Most conveniently the cam may be formed from a fiat plate,curved to define the crown 284. To facilitate bending the plate, it maybe split at the inner boundary of the crown, as indicated at 331 (Figs.26, 27). In this way, formation of the crown out of the main plane ofthe cam normal to its axis is facilitated. Provisions are made to adjustthe spacing of the axis 2I2 with relation to the axis I39 so as topredetermine the depth of the notches I86 and I81 (Fig. 29).

For this purpose the frame 281 is not rigidly attached to the frameI35-I36. Instead, this frame is adjustably mounted on carriage I35-I38.The right hand leg of frame 281 carries a boss 2I8 at its upper end,into which is fixed a guiding rod 2I5 having an axis at right angles tothe axis of the cam I88, and disposed above this axis I39.

The guide rod 2I5 is guided in appropriate apertures 2I9 and 228 (Fig.9). Aperture 2I9 is formed in a boss on the rear wall I31 of thecarriage, and aperture 228 is formed in the integral extension 338 ofboss I4I. The left hand leg of frame 281 is similarly provided with ahub 2I1, which has an internal thread, engaged by an adjusting or leadscrew 2H1. This screw 2I4 is provided with a knurled head 2 I8 (Fig. 9).The head 2I8 has an integral collar 22I for restraining the screw 2I4from axial movement. This screw is journaled at one end in the arm 222formed integrally with the boss I48 of the carriage I35-I38. The otherend of the screw 2I4 is similarly journaled in the rear wall I31 of thecarriage I38-I31. It is further restrained against axial movement by theaid of the nuts By rotation of the knurled handle 2| 8 the U-shapedframe 281 may be adjusted to bring the axis of the cam followers towardand away from the axis I 39 of the cam I88. If desired a scale andpointer may be provided to indicate the corresponding depth of theV-notches cut to correspond with the particular setting of the frame281. For this purpose a scale plate 224 (Figs. 8, 9 and 10) is supportedupon the carriage I35I38 and provided with index marks 225 at its lefthand edge. Cooperating with these index marks is a pointer 228 markedupon the lateral extension 221 of the hub 2I1.

The diagonal cuts forming the V-shaped notches I88 and I81 (Fig. 29)correspond in direction to the resultant of two component motions. Oneof these component motions is the lateral movement of the carriageI36--I36. The other motion is that of rotation of the tire I. Thedirection of the diagonal portions of the groove is thus dependent uponthe relative speeds of these two components.

In order that the groover knife 4 perform its cutting operation in thediagonal directions corresponding to the notches, the plane of thecutting edge I (Fig. 13) of this groover knife must be'adjusted so as tobe substantially normal to the resultant relative direction of the knifestructure and the tire. Accordingly provisions are made for rotating thesleeve 90 that carries the groover knife 4 in synchronism with thechanges in direction of the cut.

For this purpose the sleeve 30 carries at its upper extremity a collar228 (Figs. 8, 9, 13 and 16) This collar has a depending flange providinga threaded aperture for the set screw 228 by the aid of which the collarmay be attached to the sleeve 90. A groove 230 is formed transversely ofthe head of the collar. Within this groove is provided a slide 23Icarrying a crank pin 232. The eccentricity of the crank pin 232 withrelation to the axis of the sleeve 80 may be adjusted by movement of theslide 23I in the slot 230. The slide may be kept in adjusted position bythe aid of the clamp screw 234. The active end of the crank pm 232 isformed as a ball 235. By imparting an appropriate force upon the ballend 235, the sleeve 90 is given an angular motion to adjust the cuttingedge I0 of the groover so that the edge I0 is in proper agreement withthe angle of the notch or other pattern of the groove being out. Or theeccentricity of crank pin 232 may be predetermined and the adjustableslide 23I omitted, the cam followers 205, 206 being adjusted inaccordance with the circumference of the tire to properly synchronizethe two motions imparted to the knife and ensure that the knife angleagrees with the angle of the groove of the pattern. a

This turning force is accomplished by the aid of a transverse channelshaped member 236. The inner surface of this channel member 236 isshaped to conform to tife ball 235. It extends transversely across thecarriage I35I36 so that the channel shaped member may be in operativerelation with the ball 235 irrespective of the adjusted position of theknife structure supporting frame I I2 laterally of the carriage.

The channel member 236 is provided with the integral arms 231 joined toa long sleeve 238. This sleeve 238 is arranged so that it may be movedfrom left to right as viewed in Fig. 13, thereby imparting a cyclicangular motion to the sleeve 90 about its axis.

For this purpose the sleeve 238 as shown most clearly in Figs. 9, 11 and13 is mounted for free rotation on a cylindrical rod 239. This rod 233is mounted adjacent the upper end of the spaced arms 240 and 24I. Thesearms are integrally joined as by the cross piece 242. At the lower endsof these arms 240 and 24I are located ears 243 pivotally mounted upon ashaft 244. This shaft is supported on the carriage I35-I36 as by the aidof the ears 245-246 formed integrally with the cross bar 241 joining thesides I35 and I36.

Angular motion of the frame including the side arms 240, 24I, aboutshaft 244 is accomplished by the periphery of the cam I88, whichcooperates with a cam follower roller 248. This cam follower roller asshown most clearly in Figs. 11 and 13, is mounted for free rotationbetween the arms 248 and 24I upon the shaft 248 supported by the arms240, 24I.

The cam configuration to effect rotation of the groover knife structureis shown to best adv ntage in Figs. 8, 26, 2'7 and 28. As viewed inFigs. 8 and 27, the cam I88 rotates in a clockwise direction. When theleading edge 250 of the crown portion 204 reaches the followers 205, 206(Fig. 10), the slope 25I of the radial cam portion arrives at the roller248 (Fig. 13). The roller dips into the low portion 340 upon continuedrotation of the cam, causing the knife structure to be rotated in acounterclockwise direction as viewed in Fig. 9. At the same time, thecrown portion 204 moves the carriage toward the right.

At this stage of operation, the right hand portion of a notch I81 (Fig.29) is being out. At the time that the crest 3 of the crown portion 204becomes active, the direction of the knife structure must again bechanged to cut the left hand portion of notch I81. The roller 248 is nowriding upon slope 342 to the high part 343. When the roller reaches thishigh part, the knife structure has been rotated in a clockwise directionsufficiently to be properly positioned to cut the left hand portion ofnotch I81. This cutting continues until the crown portion 204 leaves itsfollowers, when the roller 248 drops down along slope 344 to theinactive portion of the cam. In this position, the knife structure is inthe straight ahead direction of Fig. 9.

The roller 248 is maintained in contact with the external periphery ofthe cam I88 by the aid of a pair of tension springs 262 and 253. Thesetension springs are anchored to the cross bar 242 at one end and areanchored as by the books 254 to the rear wall I31 of the carriageI35-I36.

The change of direction of the cutting edge I0 of the groover knife isquite abrupt at the tips of the notches I 81 and at the bases of thenotches. There is a corresponding resistance to the turning of thisstructure by the rubber being cut Accordingly the initiation of theknife structure turning forces and the rate of rotation are designed tooccur in such timed relation as to compensate for the reaction of therubber on the knife structure. The exact configuration of the slopingportions 25I, 342, 344, as well as their exact angular relations, areachieved by a process of trial and error.

Similar considerations apply to the exact configuration of the crownportion 204. Here again the resistance or reaction of the rubber againsttransverse motion of the knife structure must be overcome by appropriateconfiguration of the cam portions.

The cam development of Fig. 28 illustrates this clearly. Thisdevelopment is taken along a cylinder coinciding with the circularportion 345 of the cam, which is intermediate the high portion 343 andthe low portion 340. For clockwise cam rotation, the crown portion 204advances toward the left. As the rubber is out along the right handportion of notch I81 (Fig. 29), the portion 348 between points 250 andthe crest 3 is active (Fig. 28). The slope of this portion is madesumciently abrupt to compensate for the reaction of the rubber againstthe left hand side of the knife structure as viewed in Fig. 9.

Now after the turn in direction of the out is made at the crest 34I, thesloping portion 341 is active. The slope of this portion is, by trialand error, less than that of portion 346, due to the different directionof the reaction of the rubber against the knife structure. This slopingpor-

